1. Field of the Invention
The present invention relates to a low-foaming silicone composition comprising an organopolysiloxane having a specific structure.
2. Description of the Prior Art
When agrichemicals are sprayed onto crops in order to kill weeds, exterminate insect pests, or prevent disease or the like, uneven adhesion of the agrichemicals to the crops can cause a deterioration in their effectiveness. Accordingly, in order to enable an agrichemical to adhere uniformly to a crop within as short a time as possible following spraying, and enable the active ingredient to penetrate into the crop leaves and the like before rain falls, a method is usually employed in which a surfactant is added as a spreading agent to an aqueous solution or aqueous dispersion of the agrichemical, thereby lowering the surface tension of the aqueous solution or aqueous dispersion.
Typical examples of the surfactants used include non-ionic surfactants such as polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers and polyoxyethylene higher fatty acid esters. Furthermore, silicone-based surfactants are also used as they offer low toxicity and a powerful surfactant action. Of such silicone-based surfactants, polyether-modified silicones with a specific structure containing a trisiloxane skeleton within the principal chain exhibit the most powerful surfactant action, and these surfactants are already in widespread use as spreading agents for agrichemicals (see patent reference 1). Moreover, although these polyether-modified silicones suffer from a deterioration in the surfactant action under conditions where the pH is either acidic or basic, this drawback can be addressed by modifying the structure of the siloxane chain (see patent reference 2).
However, because aqueous solutions and aqueous dispersions of agrichemicals containing these types of spreading agents have a reduced surface tension, they tend to be prone to foaming. As a result, in order to prevent such foaming, an antifoaming agent is usually added during preparation of aqueous solutions or aqueous dispersions of agrichemicals. However, because the above agrichemical spreading agents, and particularly polyether-modified silicones, exhibit a powerful surfactant action, achieving complete suppression of foaming is difficult even when an antifoaming agent is added.
Moreover, if a large quantity of antifoaming agent is added in order to achieve a satisfactory antifoaming effect, then the effects of the spreading agent or the agrichemical itself may be impaired. Consequently, an agrichemical spreading agent that exhibits a powerful surfactant action but minimal foaming has been keenly sought.
In order to address the problems described above, a low-foaming spreading agent composition comprising a glycerol-modified organopolysiloxane has been proposed (see patent reference 3). However, although this composition exhibits excellent foam suppression properties, its ability to break down foam that has already formed, namely its foam-breaking properties, are inadequate.
Furthermore, because of their powerful surfactant action, silicone-based surfactants are also used in all manner of cleaning agents. For example, silicone-based surfactants can be used for cleaning the production apparatus and product-holding tank used during the production of an emulsion. Excessive foaming similar to that described above is also a problem in these types of applications.
[Patent Reference 1] EP 0 355 650 A2
[Patent Reference 2] U.S. Pat. No. 6,300,283 B1
[Patent Reference 3] JP 2005-336266 A